This invention relates generally to a magnetically synchronized clutch apparatus adapted for use in a four-wheel-drive transfer case. More particularly, it relates to such an apparatus which includes an electromagnetic synchronizer in combination with a spring-loaded jaw clutch.
A four-wheel-drive vehicle typically includes a transfer case for the delivery of power to the front and rear wheels. The transfer case generally delivers power directly to one axle, usually the rear axle, and includes a clutch which is engageable for the delivery of power to the front axle. The vehicle may be equipped with automatic wheel hubs which lock the front wheels to the front axle upon initial rotation thereof.
Under normal operating conditions, the vehicle is driven in the two-wheel-drive operating mode; that is, with power delivered to the rear driveline only. The front driveline is stationary, with the automatic wheel hubs unlocked. In this operating mode maximum fuel economy may be achieved.
When driving conditions require use of the four-wheel-drive operating mode, the transfer case clutch is engaged so as to deliver power to the front driveline. Upon initial rotation of the front axle, the wheel hubs lock to complete the torque delivery path to the front wheels. A disadvantage of this arrangement is that the clutch cannot be engaged at any appreciable vehicle speed without risking damage and/or a potentially dangerous condition, because at such a speed the rear driveline is rotating rapidly and the front driveline is stationary. The vehicle must be moving slowly (below approximately 5 mph) if the clutch is to be engaged without such risks, and without the expenditure of undue force by the vehicle operator.
There is a need in the art for a clutch apparatus which overcomes this disadvantage by being engageable safely at any vehicle speed, and which is fully engageable without necessitating extraordinary effort by the vehicle operator.